The cooking of potato chips, corn chips, chicken, meat balls and the like in a hot oil bath causes a mist to be generated over the bath. This mist includes hydrocarbons, particulates, oil droplets, smoke, water released from the food product as well as fats and other carbonaceous and odor creating elements released during the cooking process. These will be called "pollutants" below. While at one time it was common to release such pollutants to the atmosphere, today's clean air requirements prescribe that a plant operator minimize to a high extent the amount of pollutants released into the environment.
To achieve a minimal release of pollutants it has been observed that improvements are required to heat exchangers used in food cooking systems for remote heating of either a cooking fluid such as oil or water or the heating of a heat transfer fluid such as a thermal oil. Such improvements should produce a result that the odors emitted from the system are greatly reduced, if not undetectable, which is the most desirable condition indicating that pollutants are at a very low acceptable level. It is believed that the delivery of a large amount of the pollutants from the cooker to the heat exchanger combustion chamber often times passes through the combustion chamber and out the exhaust stack leaving a telltale smell in the vicinity of the plant and this is objectionable. The flow of gases in the combustion chamber, it is believed, is in a laminar pattern which tends to minimize mixing of the pollutants with the combustion gases. Thus, improvements in the combustion chamber design should ideally give a higher measure of mixing such as generating a greater amount of turbulent flow of the pollutant vapors and the combustion products so that a very minimum of odor is detectable issuing from the heat exchanger stack. A known parameter for dwell time or residence time of gases in a combustion chamber is three-tenths of a second at 1400.degree. F. and, when products are held for this time in the combustion chamber, thorough treatment and odor reduction is achieved provided there is sufficient turbulence to ensure mixing of the pollutants and combustion gases.